Ducted fan vehicles particularly useful as vtol aircraft

ABSTRACT

A vehicle, particularly a VTOL air vehicle, includes a duct carried by the vehicle frame with the longitudinal axis of the duct perpendicular to the longitudinal axis of the vehicle frame; a propeller rotatably mounted within the duct about the longitudinal axis of the duct to force an ambient fluid, e.g. air, therethrough from its inlet at the upper end of the duct through its exit at the lower end of the duct, and thereby to produce an upward lift force applied to the vehicle; and a plurality of spaced vanes pivotally mounted to and across the inlet end of the duct about pivotal axes perpendicular to the longitudinal axis of the duct and selectively pivotal to produce a desired horizontal control force in addition to the lift force applied to the vehicle. In a described preferred embodiment, the vanes are substantially parallel to the longitudinal axis of the vehicle frame. Various vane arrangements are disclosed for producing side, roll, pitch and yaw movements of the vehicle.

FIELD AND BACKGROUND OF THE INVENTION

[0001] The present invention relates to ducted fan vehicles, andparticularly to such vehicles useful as VTOL (Vertical Take-Off andLanding) aircraft.

[0002] Many different types of VTOL aircraft have been proposed wherethe weight of the vehicle in hover is carried directly by rotors orpropellers, with the axis of rotation perpendicular to the ground. Onewell known vehicle of this type is the conventional helicopter whichincludes a large rotor mounted above the vehicle fuselage. Other typesof vehicles rely on propellers that are installed inside circularcavities, shrouds, ducts or other types of nacelle, where the propelleror rotor is not exposed, and where the flow of air takes place insidethe circular duct. Most ducts have uniform cross-sections with the exitarea (usually at the bottom of the duct when the vehicle is hovering)being similar to that of the inlet area (at the top of the duct). Someducts, however, are slightly divergent, having an exit area that islarger than the inlet area, as this was found to increase efficiency andreduce the power required per unit of lift for a given inlet diameter.Some ducts have a wide inlet lip in order to augment the thrustobtained, especially in hover.

[0003] VTOL vehicles are usually more challenging than fixed wingaircraft in terms of stability and control. The main difficulty risesfrom the fact that, contrary to fixed wing aircraft which accelerate onthe ground until enough airspeed is achieved on their flight surfaces,VTOL vehicles hover with sometimes zero forward airspeed. For thesevehicles, the control relies on utilizing the rotors or propellersthemselves, or the flow of air that they produce to create controlforces and moments and forces around the vehicle's center of gravity(CG).

[0004] One method, which is very common in helicopters, is tomechanically change, by command from the pilot, the pitch of therotating rotor blades both collectively and cyclically, and to modifythe main thrust as well as moments and/or inclination of the propeller'sthrust line that the propeller or rotor exerts on the vehicle. Some VTOLvehicles using ducted or other propellers that are mounted inside thevehicle also employ this method of control. Some designers choose tochange only the angle of all the blades using ducted or other propellersthat are mounted inside the vehicle for this method of control. Theangle of all the blades may be changed simultaneously (termed collectivecontrol) to avoid the added complexity of changing the angle of eachblade individually (termed cyclic control). On vehicles using multiplefans which are relatively far from the CG, different collective controlsettings can be used on each fan to produce the desired control moments.

[0005] The disadvantage of using collective controls, and especiallycyclic controls, lies in their added complexity, weight and cost.Therefore, a simple thrust unit that is also able to generate momentsand side forces, while still retaining a simple rotor not needing cyclicblade pitch angle changes, has an advantage over the more complexsolution. The main problem is usually the creation of rotational momentsof sufficient magnitude required for control.

[0006] One traditional way of creating moments on ducted fans is tomount a discrete number of vanes at or slightly below the exit sectionof the duct. These vanes, which are immersed in the flow exiting theduct, can be deflected to create a side force. Since the vehicle'scenter of gravity is in most cases at a distance above these vanes, theside force on the vanes also creates a moment around the vehicle's CG.

[0007] However, one problem associated with vanes mounted at the exit ofthe duct in the usual arrangement as described above, is that even ifthese are able to create some moment in the desired direction, theycannot do so without creating at the same time a significant side forcethat has an unwanted secondary effect on the vehicle. For such vanesmounted below the vehicle's CG (which is the predominant case inpractical VTOL vehicles), these side forces cause the vehicle toaccelerate in directions which are usually counter-productive to theresult desired through the generation of the moments by the same vanes,thereby limiting their usefulness on such vehicles.

[0008] The Chrysler VZ-6 VTOL flying car uses vanes on the exit side ofthe duct, together with a small number of very large wings mountedoutside and above the duct inlet area.

[0009] However, in the VZ-6, the single wing and the discrete vanes wereused solely for the purpose of creating a steady, constant forwardpropulsive force, and not for creating varying control moments as partof the stability and control system of the vehicle.

[0010] The Hornet unmanned vehicle developed by AD&D, also experimentedwith using either a single, movable large wing mounted outside and abovethe inlet, or, alternatively using a small number of vanes close to theinlet side. However these were fixed in angle and could not be moved inflight.

[0011] Another case that is sometimes seen is that of vanes installedradially from the center of the duct outwards, for the purpose ofcreating yawing moments (around the propeller's axis).

OBJECTS AND BRIEF SUMMARY OF THE INVENTION

[0012] One object of the present invention is to provide a vehicle witha ducted fan propulsion system which also produces rotary moments andside forces for control purposes. Another object of the invention is toprovide a vehicle of the foregoing type particularly useful for VTOLaircraft.

[0013] According to a broad aspect of the present invention, there isprovided a vehicle, comprising: a vehicle frame; a duct carried by thevehicle frame with the longitudinal axis of the duct perpendicular tothe longitudinal axis of the vehicle frame; a propeller rotatablymounted within the duct about the longitudinal axis of the duct to forcean ambient fluid therethrough from its inlet at the upper end of theduct through its exit at the lower end of the duct, and thereby toproduce an upward lift force applied to the vehicle; and a plurality ofspaced vanes pivotally mounted to and across the inlet end of the ductabout pivotal axes perpendicular to the longitudinal axis of the ductand selectively pivotal about their axes to produce a desired horizontalcontrol force in addition to the lift force applied to the vehicle.

[0014] It has been found that such a vehicle equipped with a pluralityof such vanes pivotally mounted across the inlet of the duct (asdistinguished from the exit end of the duct) can indeed produce acombination of side forces with rotational moment that is favorable tothe normal control of the vehicle. It has also been found that suchvanes across the inlet end of the duct, particularly when combined witha second plurality of vanes across the outlet end of the duct, canproduce desired forward, aft, left and right translation movements, aswell as yaw, pitch and roll rotary movement of the vehicle.

[0015] In some described preferred embodiments, the vanes aresubstantially parallel to the longitudinal axis of the vehicle frame.

[0016] Another embodiment is described wherein the vanes include a firstgroup of parallel vanes extending across one half of the inlet of theduct and pivotal about axes at a predetermined acute angle with respectto the longitudinal axis of the vehicle frame; and a second group ofparallel vanes extending across the remaining half of the inlet end ofthe duct and pivotal about axes at the predetermined angle, but in theopposite direction, with respect to the longitudinal axis of the vehicleframe; the first and second groups of vanes being selectively pivotal toproduce a desired net control force in addition to the lift forceapplied to the vehicle.

[0017] According to further features in the described preferredembodiments, the vanes have a symmetrical airfoil shape and are spacedfrom each other a distance approximately equal to the chord length ofthe vanes.

[0018] In one described preferred embodiment, each of the vanes ispivotally mounted as a unit for its complete length to produce a desiredside force component. In a second described embodiment, each of thevanes is split into two halves, each half of all the vanes beingseparately pivotal from the other half of all the vanes, whereby thecomponent force to the lift force applied to the vehicle is a rotarymoment force about the duct longitudinal axis.

[0019] Other embodiments are described wherein, in one case, each of thevanes is pivotally mounted about an axis passing through the vane, andin another case, each of the vanes includes a fixed section and apivotal section pivotally mounted at the trailing side of the fixedsection.

[0020] According to further features in some described preferredembodiments, the duct includes a second plurality of parallel, spacedvanes pivotally mounted to and across the inlet end of the duct aboutpivotal axes perpendicular to the pivotal axes of the first-mentionedplurality of vanes and perpendicular to the longitudinal axis of theduct.

[0021] In one described preferred embodiment, the pivotal axes of thesecond plurality of vanes are in a plane vertically spaced from thepivotal axes of the first-mentioned plurality of vanes; whereas in asecond described embodiment, the pivotal axes of the second plurality ofvanes are in a common plane with that of the pivotal axes of thefirst-mentioned plurality of vanes. With respect to the latterembodiment, it may be desirable to have a slight shift in the two planesin order to offset the pivotal mounting of the vanes, but in such case,the shift would be relatively small, e.g., less than one chord length.

[0022] Another embodiment is described wherein the duct includes asecond plurality of spaced vanes pivotally mounted to and across theexit end of the duct about pivotal axes perpendicular to thelongitudinal axis of the duct and selectively pivotal about their axesto produce another desired side control force or rotary moment controlforce, in addition to the lift force applied to the vehicle.

[0023] Since the foregoing features of the invention are especiallyuseful with respect to VTOL aircraft vehicles, the invention isdescribed below particularly with respect to such vehicles, but it willbe appreciated that the invention, or various features thereof, couldalso be advantageously used in other vehicles, such as sea vehicles.

[0024] Further features and advantages of the invention will be apparentfrom the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

[0026]FIG. 1 illustrates one form of VTOL aircraft vehicle constructedin accordance with present invention;

[0027]FIG. 2 illustrates only one of the ducted fans in the aircraft ofFIG. 1;

[0028]FIG. 3 is a sectional view along line III-III of FIG. 2;

[0029]FIG. 4 is a diagram illustrating the positioning of the vanes ofFIG. 3 in one direction to produce a lateral force in one direction.

[0030]FIG. 5 is a diagram illustrating the positioning of the vanes ofFIG. 3 to produce a lateral force in the opposite direction.

[0031]FIG. 6 illustrates a modification in the construction of the vaneswherein each of the vanes is split into two halves, each half of all thevanes being separately pivotal from the other half of all the vanes toproduce a rotary moment force about the duct longitudinal axis;

[0032]FIG. 7 is a diagram illustrating the construction of one of thevanes and the manner for pivoting it;

[0033]FIG. 8 illustrates an alternative construction of one of the vanesand the manner for pivoting it;

[0034]FIG. 9 illustrates one arrangement that may be used for providingtwo cascades or assemblies of vanes at the inlet end of the duct of FIG.9;

[0035]FIG. 10 illustrates another arrangement that may be used forproviding two cascades or assemblies of vanes at the inlet end of theduct;

[0036]FIG. 11 illustrates a VTOL aircraft vehicle including a singleducted fan for propulsion and control purposes;

[0037]FIG. 12 is a view similar to that of FIG. 3 but illustrating theprovision of a cascade or plurality of vanes also at the exit end of theduct;

[0038]FIGS. 13a-13 d illustrate various pivotal positions of the twocascades of vanes in the ducted fan of FIG. 12, and the forces producedby each such positioning of the vanes;

[0039]FIG. 14 is a top view diagrammatically illustrating anotherconstruction wherein the vanes extending across the inlet of the ductare divided into two groups together producing the desired nethorizontal control force;

[0040]FIGS. 15a and 15 b diagrammatically illustrate the manner in whichthe desired net horizontal control force is produced by the vanes ofFIG. 14; and

[0041]FIG. 16 is a view corresponding to that of FIG. 14 butillustrating a variation in the vane arrangement for producing thedesired net horizontal control force.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0042] The vehicle illustrated in FIG. 1, and therein generallydesignated 2, is a VTOL aircraft including a frame or fuselage 3carrying a ducted fan propulsion unit 4 at the front, and anothersimilar propulsion unit 5 at the rear. The vehicle payload is shown at 6and 7, respectively, on opposite sides of the fuselage, and the landinggear as shown at 8.

[0043]FIGS. 2 and 3 more particularly illustrate the structure ofpropulsion unit 4, which is the same as propulsion unit 5. Such apropulsion unit includes a duct 10 carried by the fuselage 3 with thevertical axis 10 a of the duct parallel to the vertical axis of thevehicle. Propeller 11 is rotatably mounted within the duct 10 about thelongitudinal axis 10 a of the duct. Nose 12 of the propeller facesupwardly, so that the upper end 13 of the duct constitutes the air inletend, and the lower end 14 of the duct constitutes the exit end. As shownparticularly in FIG. 3, the upper air inlet end 13 is formed with afunnel-shaped mouth to produce a smooth inflow of air into the duct 10,which air is discharged at high velocity through the exit end 14 of theduct for creating an upward lift force.

[0044] To provide directional control, the duct 10 is provided with aplurality of parallel, spaced vanes 15 pivotally mounted to, and across,the inlet end 13 of the duct. Each of the vanes 15 is pivotal about anaxis 16 perpendicular to the longitudinal axis 10 a of the duct 10 andsubstantially parallel to the longitudinal axis of the vehicle frame 2,to produce a desired horizontal control force in addition to the liftforce applied to the vehicle by the movement of air produced by thepropeller 11. Thus, as shown in FIG. 4, if the vanes 15 are pivoted inone direction about their respective axes, they produce a desiredcontrol force in the direction of the arrow F1 in FIG. 4; and if theyare pivoted in the opposite direction, they produce a desired controlforce in the direction of the arrow F2 in FIG. 5. As shown in FIG. 3(also FIGS. 7, 8, 12), the vanes 15 are of a symmetric airfoil shape andare spaced from each other a distance approximately equal to the chordlength of the vanes.

[0045]FIG. 6 illustrates a variation wherein each of the vanes 15,instead of being pivotally mounted as a unit for its complete length toproduce the desired side control force is split into two half-sections,as shown at 15 a and 15 b in FIG. 6, with each half-section separatelypivotal from the other half-section. Thus, all the half-sections 15 amay be pivoted as a unit in one direction as shown by arrow D₁, and allthe half-sections 15 b may be pivoted in the opposite direction as shownby arrow D₂, to thereby produce any desired side force or rotary momentin addition to the lift force applied to the vehicle by the propeller.

[0046] As shown in FIG. 7, each of the vanes 15 is pivotally mountedabout axis 16 passing through a mid portion of the vane. FIG. 8illustrates a modification wherein each vane includes a fixed section17, which constitutes the main part of the vane, and a pivotal sectionor flap 18 pivotally mounted at 19 to the trailing side of the fixedsection. It will thus be seen that the pivotal section or flap 18 may bepivoted to any desired position in order to produce the desired controlforce in addition to the lift.

[0047]FIG. 9 illustrates a variation wherein the ducted fan (4 and/or 5FIG. 1) includes a second plurality or cascade of parallel, spacedvanes, one of which is shown at 20, pivotally mounted to and across theinlet end 13 of the duct 10. Thus, each of the vanes 20 of the secondplurality is closely spaced to the vanes 15 and is pivotal about an axisperpendicular to the pivotal axis of the vanes 15, as well as to thelongitudinal axis 10 a of the duct.

[0048] In the variation illustrated in FIG. 9, the two cascades of vanes15, 20, are arranged in parallel, spaced planes. FIG. 10 illustrates avariation wherein the two cascades of vanes at the inlet end of the ductare intermeshed. For this purpose, each of the vanes 21 of the secondplurality would be interrupted so as to accommodate the crossing vanes15 of the first plurality, as shown in FIG. 10. Another possiblearrangement would be to have the vanes of both cascades interrupted forpurposes of intermeshing.

[0049]FIG. 11 illustrates a VTOL aircraft vehicle, therein generallydesignated 22, including a single ducted fan 24 carried centrally of itsfuselage 23. Such a vehicle could include the arrangement of vanesillustrated in either FIG. 9 or in FIG. 10 to provide the desiredcontrol forces and moments in addition to the lift forces. In such avehicle, the payload may be on opposite sides of the central ducted fan24, as shown at 25 and 26 in FIG. 11. The vehicle may also include otheraerodynamic surfaces, such as rudders 27, 28 to provide steering andother controls.

[0050]FIG. 12 illustrates a further embodiment that may be included ineither of the vehicles of FIGS. 1 and 11 wherein the duct 10 also has asecond plurality or cascade of parallel, spaced vanes, but in this case,the second plurality are pivotally mounted to and across the exit end 14of the duct 10. Thus, as shown in FIG. 12, the duct 10 includes thefirst plurality or cascade of blades 15 mounted to and across the inletend 13 of the duct, and a second plurality or cascade of blades 35mounted to and across the exit end 14 of the duct 10, also perpendicularto the longitudinal axis of the duct and substantially parallel to thelongitudinal axis of the vehicle frame. Each assembly or cascade 15, 35of the vanes may be pivoted independently of the other to produceselected side forces or rotary moments about the duct's transverse axis10 b for pitch or roll control of the vehicle.

[0051] This is more clearly shown in the diagrams of FIGS. 13a-13 d.Thus, when the two cascades of vanes 15, 35, are pivoted in oppositedirections, they produce a rotary moment about the transverse axis 10 bof the duct 10 in one direction (e.g., counter-clockwise as shown inFIG. 13a); when they are pivoted in the same direction, they produce aside force in one direction (e.g. left) as shown in FIG. 13b whenpivoted in opposite directions but opposite to the arrangement shown inFIG. 13a, they produce a rotary moment in the opposite clockwisedirection as shown in FIG. 13c; and when they are pivoted in the samedirection but opposite to that shown in FIG. 13b, they produce a sideforce in the opposite (e.g. right) direction, as shown in FIG. 13d.

[0052]FIG. 14 is a top view illustrating another construction of ductedfan propulsion unit, generally designated 20, including a duct 22 havinga plurality of vanes 24 extending across the inlet end of the duct. Inthis case, the vanes 24 are divided into a first group of parallel vanes24 a extending across one-half the inlet end of the duct 22, and asecond group of parallel vanes 24 b extending across the remaining halfof the inlet end of the duct.

[0053]FIG. 14 also illustrates the nose 26 of the propeller within theduct 22. The propeller is rotatably mounted within the duct 22 about thelongitudinal axis of the duct, with the nose 26 of the propellercentrally located at the air inlet end of the duct such that the airdischarged at a high velocity through the opposite end of the ductcreates an upward lift force.

[0054] As shown in FIG. 14, the first group of parallel vanes 24 aextending across one half of the inlet end of the duct 22 are pivotalabout axes 25 a at a predetermined acute angle α with respect to thelongitudinal axis 20 a of the vehicle frame and thereby of the directionof movement of the vehicle as shown by arrow 27; and that the secondgroup of parallel vanes extending across the remaining half of the inletend of the duct are pivotal about axes 25 b at the same predeterminedangle α, but in the opposite direction, with respect to the longitudinalaxis 20 a of the vehicle frame. The two groups of vanes 24 a, 24 b areselectively pivotal to produce a desired net horizontal control force inaddition to the lift force applied to the vehicle.

[0055] The foregoing operations are illustrated in the diagrams of FIGS.15a and 15 b. Both FIGS. 15a and 15 b illustrate the control forcesgenerated when the vehicle includes two ducted fan propulsion units 20,30, at the opposite ends of the vehicle and coaxial with the vehiclelongitudinal axis 20 a. It will be appreciated that comparable forcesare produced when the vehicle is equipped with only one ducted fanpropulsion unit shown in FIG. 14.

[0056]FIG. 15a illustrates the condition wherein the two groups of vanes24 a, 24 b are pivoted to equal angles about their respective axes. Thevanes thus produce, in addition to the lift force, control forces ofequal magnitude and angles on opposite sides of the vehicle longitudinalaxis 20 a, so as to produce a net force, shown at Fa, coaxial with thevehicle longitudinal axis 20 a.

[0057] The two groups of vanes 34 a, 34 b of the rear propulsion unit 30are pivotal in the same manner about their respective pivotal axes andthereby produce a net force Fa also coaxial with the vehiclelongitudinal axis 20 a.

[0058]FIG. 15b illustrates a condition wherein the two groups of vanes24 a, 24 b in the fore propulsion unit 20, and the two groups of vanes34 a, 34 b in the aft propulsion unit 30, are pivoted about theirrespective axes to unequal angles, thereby producing net side forces Fbat an angle to the vehicle longitudinal axis 20 a. Thus, by controllingthe pivot angles of the vanes 24 a, 24 b and 34 a, 34 b about theirrespective pivotal axes, a net control force may be generated as desiredin the plane of the vanes.

[0059]FIG. 16 illustrates a ducted fan propulsion unit, generallydesignated 40, also including two groups of vanes 44 a, 44 b, extendingacross one-half of the inlet of the duct 42 and pivotally mounted aboutaxes 45 a, 45 b at a predetermined angle, (e.g., 45°) to thelongitudinal axis 40 a of the vehicle. In this case, however, the vanes44 a, 44 b are oriented in the forward direction, rather than in the aftdirection as in FIG. 14, but the operation, and the forces generated bythe vanes, are basically the same as described above with respect toFIGS. 14, 15a, 15 b.

[0060] It will be appreciated that any of the foregoing arrangements ofFIGS. 14-16, as well as those of FIGS. 1-11, could also be provided atthe exit ends of the ducts, as shown in FIGS. 12-13 d, to produce thedesired control forces in addition to the lift forces. The vanes are notintended to block air flow, but merely to deflect air flow to producethe desired control forces. Accordingly, in most applications the vaneswould be designed to be pivotal no more than 15° in either direction,which is the typical maximum angle attainable before flow separation.

[0061] Since the control forces and moments are generated by horizontalcomponents of the lift forces on the vanes themselves, the vanes shouldpreferably be placed on the intake side of the propeller as far from thecenter of gravity of the vehicle as possible for creating the largestattainable moments. The same applies if vanes are provided on the exitside of the ducts.

[0062] While the invention has been described above particularly withrespect to air vehicles, it will be appreciated that the invention, orvarious aspects of the invention as described above, can also beadvantageously used with other types of vehicles such as sea vehicles,to provide propulsion and directional control to the vehicle.

[0063] Accordingly, while the invention has been described with respectto several preferred embodiments, it will be understood that these areset forth merely for purposes of example, and that many othervariations, modifications and applications of the invention may be made.

1. A vehicle, comprising: a vehicle frame; a duct carried by saidvehicle frame with the longitudinal axis of the duct perpendicular tothe longitudinal axis of the vehicle frame; a propeller rotatablymounted within said duct about the longitudinal axis of the duct toforce an ambient fluid therethrough from its inlet at the upper end ofthe duct through its exit at the lower end of the duct, and thereby toproduce an upward lift force applied to the vehicle; and a plurality ofparallel, spaced vanes pivotally mounted to and across the inlet end ofthe duct about pivotal axes perpendicular to said longitudinal axis ofthe duct and substantially parallel to said longitudinal axis of thevehicle frame, said vanes being selectively pivotal about their axes toproduce a desired horizontal force component to the lift force appliedto the vehicle.
 2. The vehicle according to claim 1, wherein said vaneshave a symmetrical airfoil shape and are spaced from each other adistance approximately equal to the chord length of the vanes.
 3. Thevehicle according to claim 1, wherein each of said vanes is pivotallymounted as a unit for its complete length to produce a desired sideforce component.
 4. The vehicle according to claim 1, wherein each ofsaid vanes is split into two halves, each half of all the vanes beingseparately pivotal from the other half of all the vanes, whereby theforce component to the lift force applied to the vehicle is a rotarymoment force about the duct longitudinal axis.
 5. The vehicle accordingto claim 1, wherein each of said vanes is pivotally mounted about anaxis passing through the vane.
 6. The vehicle according to claim 1,wherein each of said vanes includes a fixed section and a pivotalsection pivotally mounted at the trailing side of the fixed section. 7.The vehicle according to claim 1, wherein said duct includes a secondplurality of parallel, spaced vanes pivotally mounted to and across saidinlet end of the duct about pivotal axes perpendicular to said pivotalaxes of the first-mentioned plurality of vanes and perpendicular to saidlongitudinal axis of the duct.
 8. The vehicle according to claim 7,wherein the pivotal axes of said second plurality of vanes are in aplane vertically spaced from the pivotal axes of said first-mentionedplurality of vanes.
 9. The vehicle according to claim 7, wherein thepivotal axes of said second plurality of vanes are in a common planewith that of the pivotal axes of said first-mentioned plurality ofvanes.
 10. The vehicle according to claim 1, wherein said vanes include:a first group of parallel vanes extending across one half of the inletof said duct and pivotal about axes at a predetermined acute angle withrespect to the longitudinal axis of the vehicle frame; and a secondgroup of parallel vanes extending across the remaining half of the inletend of said duct and pivotal about axes at said predetermined angle, butin the opposite direction, with respect to the longitudinal axis of thevehicle frame; said first and second groups of vanes being selectivelypivotal to produce a desired net control force in addition to the liftforce applied to the vehicle.
 11. The vehicle according to claim 10,wherein said predetermined angle is 45°.
 12. The vehicle according toclaim 1, wherein said duct includes a second plurality of parallel,spaced vanes pivotally mounted to and across said exit end of the ductabout pivotal axes perpendicular to said longitudinal axis of the ductand substantially parallel to said longitudinal axis of the vehicleframe to thereby produce a desired side force component, or a rotarymoment force component about the duct transverse axis, to the lift forceapplied to the vehicle.
 13. The vehicle according to claim 12, whereinsaid vanes in both of said plurality have a symmetrical airfoil shapeand are spaced from each other a distance approximately equal to thechord length of the vanes in the second plurality of vanes.
 14. Thevehicle according to claim 1, wherein said duct, propeller and pluralityof vanes are carried by said vehicle at one end of the vehicle, and saidvehicle includes a second duct, propeller and plurality of vanes at theopposite end of the vehicle.
 15. The vehicle according to claim 1,wherein the vehicle carries the duct, propeller and plurality of vanesat the center of the vehicle.
 16. The vehicle according to claim 1,wherein the vehicle is a VTOL air vehicle.
 17. A VTOL-air vehicle,comprising: a vehicle frame; a duct carried by said vehicle frame withthe longitudinal axis of the duct perpendicular to the longitudinal axisof the vehicle frame; a propeller rotatably mounted within said ductabout the longitudinal axis of the duct to force air therethrough fromits inlet at the upper end of the duct through its exit at the lower endof the duct, and thereby to produce an upward lift force applied to thevehicle; and a plurality of parallel, spaced vanes pivotally mounted toand across the inlet end of the duct about pivotal axes perpendicular tosaid longitudinal axis of the duct and substantially parallel to saidlongitudinal axis of the vehicle frame, said vanes being selectivelypivotal along their axes to produce a desired horizontal force componentto the lift force applied to the vehicle.
 18. The VTOL air vehicleaccording to claim 17, wherein said vanes have a symmetrical airfoilshape and are spaced from each other a distance approximately equal tothe chord length of the vanes.
 19. The VTOL air vehicle according toclaim 17, wherein each of said vanes is pivotally mounted as a unit forits complete length to produce a desired side force component.
 20. TheVTOL air vehicle according to claim 17, wherein said duct includes asecond plurality of parallel, spaced vanes pivotally mounted to andacross said exit end of the duct about pivotal axes perpendicular tosaid longitudinal axes of the duct and vehicle frame to thereby producea desired side force component, or a rotary moment force component aboutthe duct transverse axis, to the lift force applied to the vehicle. 21.The VTOL air vehicle according to claim 20, wherein said duct, propellerand plurality of vanes are carried by said vehicle at one end of thevehicle, and said vehicle includes a second duct, propeller andplurality of vanes at the opposite end of the vehicle.
 22. The VTOL airvehicle according to claim 20, wherein the vehicle carries the duct,propeller and plurality of vanes at the center of the vehicle.